1. Field of the Invention
The present invention relates to a lubricant. More particularly, the present invention relates to a Flon-free lubricant for wire feeding and wire drawing and also to a welding wire coated with said lubricant and produced by the used of said lubricant.
2. Description of the Prior Art
Welding wires (including solid wires and cored wires) are manufactured by the wire-drawing process which employs dies and rollers. Therefore, they have minute irregularities on their surface in the longitudinal and circumferential directions. These minute irregularities have an adverse effect on the feeding of the welding wire to the welding torch through the conduit tube and also on the electrical conductivity between the welding wire and the tip. The adverse effect of minute irregularities on the wire surface is reduced conventionally by coating the wire surface with a powder of polytetrafluoroethylene (abbreviated as PTFE hereinafter). (See Japanese Patent Publication No. 17638/1982.)
According to the conventional practice, the coating of the wire surface with PTFE powder is accomplished by dipping the wire in a solvent dispersion of PTFE powder, followed by drying for solvent removal. The dispersing medium for PTFE powder is Flon-113, which is a fluorocarbon solvent. This solvent is most desirable because it contains no hydrogen and dries fast.
It has recently been considered that Flon-113 destroys the ozone layer. This has moved UNEP (United Nations Environment Programme) to regulate the use of Flon-113. The Montreal Protocol declares the ban of Flon-113 after the year 2000. Under these circumstance, it is an urgent necessity to develop a substitute for PTFE dispersion in Flon.
PTFE dispersion in Flon is used mainly as a lubricant for wire feeding. It is also used as a lubricant for wire drawing. Its use as a lubricant poses the problem associated with the destruction of the ozone layer.